It is known that an ester compound or an amide compound of an o-naphthoquinonediazidosulfonic acid is employed as a photosensitive composition. These compounds are widely used in the industries for the production of lithographic printing plates, in particular, the so-called presensitized plates which comprise a coating of a photosensitive composition previously applied to a support (usually referred to as PS plates) or as photoresist materials for letterpress printing plates, IC circuits, photomasks or printed wirings.
However, the photosensitive compositions containing an o-naphthoquinonediazide compound have the following drawbacks. That is, when a photosensitive o-naphthoquinonediazide compound having yellow color is exposed to light, the compound is subjected to fading to form a colorless or light-yellow colored photodecomposition product, and under a yellow safety light in exposure work, however, the exposed portions and unexposed portions can not be discriminated. Thus, it is impossible to determine, for example, whether the printing plate has been exposed or not in the event that printing work is interrupted when simultaneously exposing many printing plates. Similarly, for example, when a large plate is repeatedly exposed for making a lithographic printing plate as in the so-called plate-setting printing method, it can not be confirmed whether and what portions were exposed. Therefore, they cause errors in the operation and result in remarkable decrease of work efficiency.
In order to eliminate these drawbacks, several attempts have been made for directly providing a visible image after the exposure of a photosensitive composition. For instance, the use of a various kind of reduction susceptive salts as shown in U.S. Pat. Nos. 2,006,913 and 2,618,555 in a mixture together with a diazo compound; the method of forming a visible image from a combination of a photosensitive diazo compound and an acid alkaline indicator as described in Japanese Patent Publication No. 2203/1965; a composition of a photosensitive positive acting diazo resin and a merocyanine dye as described in Japanese Patent Publication No. 3041/1974; a printing plate previously sensitized with an o-naphthoquinonediazide which contains uniform particles of an organic coloring agent which changes its color in a pH range of 2.5 to 6.5 in a photosensitive layer thereof as described in Japanese Patent Publication No. 21093/1965; a photosensitive duplicating layer of an ester or amide of an o-naphthoquinonediazidosulfonic acid which contains an o-naphthoquinonediazido-4-sulfonic acid halogenide and an organic compound capable of forming a salt as a dye in the ranges of 10 to 75% by weight and 1 to 50% by weight based on the total amount of the o-naphthoquinonediazide compound, respectively as described in Japanese Patent Application (OPI) No. 36209/1975; a mixture of an ester compound of a phenol substituted with an electron attractive substituent and o-naphthoquinonediazido-4-sulfonic acid and an organic dye which changes its color tone upon the interaction with a photodecomposition product of the o-naphthoquinonediazide compound as described in British Patent Publication No. 2,038,801A, or the like.
However, even in these cases in which such an improvement has been performed, the contrast of a visible image obtained by exposure is insufficient for practical working under a yellow safety light in most cases and, thus, it does not reach a level at which the above described plate-setting printing work can be conducted without hindrance. Also, it is usually observed that the physical properties and the developing property of the photosensitive layer are largely influenced even when a sufficient contrast is obtained. Further, the sufficient contrast is not obtained after the storage for a long period of time and therefore, satisfactory results can not be obtained at present.